It is well known that boats can be propelled
heteronomously (such as by a sail)
autonomously (where the source of energy is generated within the boat) such as by water jet propulsion or by a marine screw propeller.
Water jet propulsion is advantageous at speeds greater than 70 knots and creates problems in the structure and system as a high rate of flow is needed for satisfactory performance.
Marine screw propulsion (from 2 to 6 blades) creates problems as, if a certain number of revolutions is exceeded, cavitation occurs with reduced thrust.
To drive the propeller alternating marine internal combustion engines cooled by sea water are generally used, but their efficiency is considerably less than that of land-based engines.
The above invention eliminates or appreciably lessens these drawbacks by means of a system which creates a high thrust and at the same time allows the boat to ride on a cushion of air as will be explained below.